But the talks reach beyond the ports, which handle more than 40 percent of U.S. waterborne trade, according to academic and industry data. A shutdown could retard the nation's economic recovery and trigger an international financial crisis, says Stephen Cohen, a professor at the University of California-Berkeley.

Fortunately, the train rarely crashes. The Longshore and Warehouse Union negotiates contracts every three years and last struck in 1971. In addition, labor negotiations are often full of dire predictions, veiled threats and fiery rhetoric yet rarely lead to walkouts.

But these negotiations appear a bit different to some, and that difference is generating fear among retailers and shippers. Among the contract topics, the Pacific Maritime Association is pushing for technological upgrades at the ports, while the union wants to make pension changes and protect traditional Longshoremen jobs from going to outsiders.

If negotiators can't settle their differences, a strike or lockout could ripple through the nation's economy, emptying store shelves and cutting into consumer spending that has helped prop up the economy, experts say.

Some of the loss estimates are staggering.

A 10-day shutdown at West Coast ports could strip $19.4 billion from the U.S. economy, Cohen wrote in a recent analysis, citing a Martin Associates study. After 20 days, the price jumps to $48.6 billion, according to the study.

Those types of estimates are making some executives nervous, leading them to spend millions of dollars on contingency plans, according to Lanier.

That's because a strike or an employer-led lockout of employees threatens to disrupt the modern inventory plans of many U.S. companies. Firms simply keep far less on their shelves than 20 years ago, according to academic observers.

"The impact would be even greater today" than the 1971 strike, said David Olson, a political science professor at the University of Washington. "Many firms in the U.S. use just-in-time delivery where their warehouse is the container box."

Some companies are moving more cargo onto dry land to prepare for a labor dispute, according to an official at a West Coast shipping concern, who requested anonymity.

Olson points out both sides have made concessions and avoided strikes and lockouts in the past because the price would have been so high.

"Agreement has been reached (in the past), and that agreement is partly because the employer has been unwilling to take a strike -- that the cost of bearing a strike is higher than the cost of coming to a settlement," Olson said.

"So the collective bargaining process has worked."

As the fifth-largest port on the West Coast, the Port of Seattle has plenty at stake. In 2001, the port handled 1.3 million containers, according to its own data.

After negotiators entered into formal talks May 13, they agreed to a media blackout. The union's contract expires July 1.

"The parties continue to communicate well with hard bargaining expected by both sides that will result in a successful contract," said a statement by the Pacific Maritime Association, which represents domestic and foreign operators, stevedores and terminal companies.

Longshoremen, meanwhile, are unified and prepared -- but not eager -- to start a fight, says Max Vekich, the president of Local 24 in Aberdeen.

"I can't see where a lockout serves anybody's agenda," Vekich, who is not a member of the negotiating team, said. "We are not going to provoke a fight."

But the Maritime Association, not the union, could decide to lock employees out of their jobs to try to secure desired changes, says Lanier of the West Coast Waterfront Association.

"Everyone now believes the unions will engage in slowdowns around the 6th of July," Lanier said. "There is a huge probability PMA is going to lock them out."

Even if talks break down, a strike or lockout is far from automatic. For example, President Bush could determine either action poses too great a threat to the economy and call for a 30- to 90-day "cooling off" period, UW's Olson said.

Bush used that power last year to order a cooling off period during Northwest Airlines negotiations.

"We are at this critical period at the economic recovery ... and any disruption would be negative," said Keitaro Matsuda, senior economist at the Union Bank of California.